ABSTRACT This project will investigate early pathophysiological hallmarks of Alzheimer's disease (AD) using newly- developed microscopy tools. Alzheimer's disease (AD) is a devastating, irreversible neurodegenerative disorder that currently has no effective treatment. Long before the first clinically-observable cognitive and behavioral symptoms of Alzheimer's disease (AD) arise, a ?preclinical? incubation phase transpires, lasting up to ~2 decades and involving a myriad of changes at the cellular and vascular level. More detailed knowledge of these intricate, multifaceted preclinical alterations and their contributions to subsequent cognitive deterioration is essential to fill critical gaps in our understanding of AD's pathogenesis and to comprehensively assess the therapeutic potential of candidate treatments. Exploring the neurovascular and metabolic alterations that occur during the preclinical phase of AD could hold the key to understanding how to detect and counteract AD- related neurodegeneration. We have developed an array of innovative optical microscopy tools to noninvasively characterize multiple facets of cerebral blood flow and energy metabolism in living animal brains. These advanced techniques are ideally suited to characterize the convoluted progression of multiple pathophysiological features of preclinical AD. Specifically, these investigations will explore on a microscopic scale how accumulation of amyloid ? and neuroinflammation, notable AD pathophysiological hallmarks, affect the neurovascular unit, cerebral oxygenation, energy metabolism, and cerebral blood flow. The results will help us understand in greater detail the multifactorial structural and functional changes that happen in the brain and collectively give rise to clinically-observable cognitive deficiencies. This project will yield insight into the mechanisms underlying AD pathogenesis with unprecedented detail, and it will facilitate the development of new therapeutic techniques widely applicable to the growing population of at-risk aging citizens.